Mikhail Baryshnikov, incapacitated by a foot injury, was unable to perform as scheduled last night with the New York City Ballet at the Kennedy Center Opera House.

According to company manager Edward Bigelow, Baryshnikov is suffering from an aggravated Achilles tendon (a painful but common ailment for dancers) that had been building up in intensity recently. He will not be in shape to undertake his slated performances tonight, Thursday and Friday evenings during this second and last week of the company's current Washington engagement.

Baryshnikov, who very seldom misses any performances, had been dancing an unusually heavy schedule last week, in his first performances in this city with the NYC Ballet since his exodus from American Ballet Theatre last spring.

During the company's opening week, he had appeared in two performances of "Prodigal Son," as well as "Four Seasons" and "Harlequinade," in addition to attending daily rehearsals in preparation for the special White House program in his honor last Sunday afternoon, at the invitation of President and Mrs. Carter. After dancing in all four works on the White House program, he went on to perform in the company's Sunday evening performance of "Harlequinade" at Kennedy Center Sunday night.

Baryshnikov was to have performed last night in "Dances at a Gathering" (he was replaced by Helgi Tomasson, and his partner Patricia McBride by Judith Fugate); tonight in "Harlequinade"; Thursday in "Other Dances"; and Friday in "Prodigal Son."

Bigelow said that Baryshnikov had been examined by the company's orthopedist, but that it was too soon to tell exactly how long the injury will take to heal.It is possible, he reported, that Baryshnikov will be unable to perform for as long as a month.